Lock wire securing method

ABSTRACT

The invention relates to a process for applying a ferrule to a lock wire and crimping the ferrule onto the lock wire. The process utilizes a lock wire having a ferrule applied to one end and which is placed through a plurality of threaded fasteners with a free end of a lock wire extending beyond the last of the threaded fasteners. The free end of the lock wire is inserted through a ferrule held in the apparatus and through a tensioning rod. Movement of the tensioning rod exerts a predetermined tension on the lock wire at which time the device crimps the ferrule onto the lock wire to retain it in place at the desired tension.

This application is a continuation of application Ser. No. 07/706,841,filed May 29, 1991, which is a division of Ser. No. 07/422,574, filedOct. 17, 1989, now Patent No. 5,052,094.

BACKGROUND OF THE INVENTION

The present invention relates to a tool for applying a ferrule to a lockwire tethering together a plurality of elements such as threadedfasteners.

In rotating machinery having close tolerances between the rotating andthe stationary portions, such as turbines, it is imperative that allobjects, no matter how small, be kept from contacting the rotatingelements of the machinery. The presence of any foreign object couldresult in the catastrophic failure of the entire rotating machinery.

Such machinery is inherently complex and requires the usage of manynuts, bolts, screws and other threaded fasteners to assemble all of thecomponents of the machine. Since the operation of such machinery mayinvolve very high rotating speeds and induce vibrations into the machineelements, it is necessary to provide some means for preventing theinadvertent unthreading of the numerous threaded fasteners.

It is known to apply lock wires to tether threaded fasteners together toprevent their inadvertent unthreading. Typically, the lock wire passesthrough a transverse hole in at least two threaded fasteners and istwisted back on itself in alternating clockwise and counterclockwisedirections between the threaded fasteners. The process is duplicatedbetween additional threaded fasteners until the entire threaded fastenerpattern has been wired. Following the required stringing and twisting,the lock wire is cut and bent into a certain position.

While the known lock wire has provided satisfactory results, it requiresa very time consuming and laborious application process. Due to thedependency upon the operators skill in twisting the lock wire, often thefinal result is unsatisfactory due to variations in the quantity andtautness of the twists, and the variations in the tension on the lockwire. It has been estimated that annual losses of approximately$10,000,000 are incurred just from re-working unacceptable lock wireassemblies.

SUMMARY OF THE INVENTION

The present invention relates to a method for applying a ferrule to alock wire, tensioning the lock wire to a pre-determined value andcrimping the ferrule onto the lock wire. The method is used with a lockwire having a ferrule applied to one end and which is threaded through aplurality of threaded fasteners with a free end of the lock wireextending beyond the last of the threaded fasteners. The free end isinserted through a ferrule (held in apparatus for installing the lockwire) and through a tensioning rod. Movement of the tensioning rodexerts a predetermined tension on the lock wire at which time the devicecrimps the ferrule onto the lock wire to retain it in place at thedesired tension. The free end of the lock wire extending beyond theattached ferrule is cut off to complete the process.

Essentially, the process involves providing first and last elements of aseries that are to be connected together, for example threadedfasteners, providing apertures in the elements for receiving a flexibletension element, threading an elongated flexible tension elementforwardly through the apertures serially from the first to the lastelement of the series, providing a first motion stopping means on afirst end of a flexible tension element for preventing forward movementof the tension element through the aperture in the first element in theseries, drawing a tension on the tension element in a forward directionfrom a location beyond the last element of the series while the firstmotion stopping means prevents forward motion of the tension elementrelative to the first element of the series, while maintaining saidtension on said flexible tension element, securing the tension elementagainst reverse longitudinal motion relative to the last element of theseries by providing a second motion stopping means permanentlyassociated with the tension element adjacent and beyond the last elementof the series, with the second motion stopping means preventing reverselongitudinal movement of the tension means through the aperture of thelast element of the series, whereby the elements of the series areconnected together.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a known lock wire.

FIG. 2 is a plan view of a lock wire applied with apparatus according tothis invention.

FIG. 3 is a top view of an applicator for carrying out the presentinvention.

FIG. 4 is a cross-sectional view taken along line 4--4 in FIG. 3.

FIG. 5 is a top view of a magazine for storing and inserting theferrules used in accordance with the invention.

FIG. 6 is an end view of the magazine viewed in the direction of arrow 6in FIG. 5.

FIG. 7 is a cross-sectional view taken along 7--7 in FIG. 5.

FIG. 8 is a partial perspective view illustrating the magazine insertinga ferrule in the applicator for carrying out the invention.

FIG. 9 is a partial, perspective view illustrating the application ofthe ferrule and the tensioning of the lock wire according to theinvention.

FIG. 10 is a perspective view of the ferrule applied to the lock wire inaccordance with the invention.

FIG. 11 is a schematic diagram of the hydraulic power supply systemassociated with the applicator for carrying out the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A known lock wire is illustrated in FIG. 1 wherein separate elementssuch threaded fasteners 10, 12 and 14 are engaged with portion 16 of therotating apparatus (not otherwise shown). The lock wire 18 comprises twostrands 18a and 18b, twisted together at one end and separated such thatstrand 18a passes through a transverse opening in fastener 10 whilestrand 18b passes around the exterior of the fastener 10. The strandsare twisted together on the opposite side of fastener 10 and passthrough a transverse opening formed in fastener 12. The lock wire 18continues until the last fastener, in this case fastener 14, whereuponone strand passes through a transverse opening in the fastener while theother strand passes around and contacts the exterior of the fastener.The strands are twisted together on the opposite side of fastener 14.

FIG. 2 illustrates a lock wire system applied using the apparatus andmethod for carrying out the process of the present invention. Threadedfasteners 10, 12 and 14 are engaged with machinery portion 16. Lock wire20 (broadly referred to as a "flexible tension element"); comprises asingle strand of wire having a ferrule 22 (herein broadly referred to asa motion stopping means); fixed to end 20a. Lock wire 20 is threadedforwardly through the transverse openings formed in the threadedfasteners 10, 12 and 14 until ferrule 22 bears against fastener 10.Ferrule 22 stops further forward motion of wire 20. At this point,ferrule 24 (also a motion stopping means) is inserted over the end ofwire 20 against fastener 14, a tension is applied to the lock wire 20and the ferrule 24 is crimped onto the lock wire such that it bearsagainst a side of fastener 14 to prevent reverse motion of wire 20. Lockwire 20 is then cut off. The predetermined tension is maintained in lockwire 20 by the contact of ferrules 22 and 24 with threaded fasteners 10and 14, respectively.

The applicator portion 26 of the apparatus for applying the ferrule tothe second end of the lock wire is referred to as an applicator tool andis illustrated in FIGS. 3 and 4; Tool 26 comprises an elongated bodyincluding housing 28 having a tension rod 30 slidably mounted therein atthe proximal end of the portion 26 and such that the end 30a of thetension rod extends axially outwardly of housing 28. End 30a defines apassage 30b from the distal end of the tension rod 30 to an uppersurface thereof outside of the housing. Tension rod 30 is mounted inhousing 28 so as to be axially movable in the directions of arrows 32generally parallel to the longitudinal axis of housing 28 extendingalong line 4--4 in FIG. 3.

Housing 28 also defines a chamber 34 in which ferrule crimper actuatorpiston 36 is slidably retained so as to be also movable in thedirections of arrows 32. Piston rod 38 extends from piston 36 and hasrear anvil retainer 40 attached thereto. Spring 39 is interposed betweenpiston rod 38 and crimp head 44 and biases the piston rod 38 toward theright as seen in FIG. 4.

Front anvil retainer 42 is arranged generally coaxially with piston rod38 and is slidaly mounted in crimp head 44 attached to housing 28.Ferrule deforming punch 46 is connected to and extends axially fromfront anvil retainer 42.

Crimp head 44 defines a ferrule retaining and supporting aperture oropening 48 at the distal end of portion 26 and a tension guide notch 50.Guide notch 50 is dimensioned to receive the lock wire 20 prior to theinsertion of the end through passage 30b of tension rod 30.

As illustrated in FIG. 4, front anvil retainer 42 is axially spaced fromrear anvil retainer 40. This spaced position is maintained by curvedspring washer 52 which biases the front anvil retainer 42 toward theleft. Additional curved spring washers 54 are located between the crimphead 44 and the front anvil retainer 42. The biasing forces of therespective spring washers 52 and 54 are selected such that when the gapis present between rear anvil retainer 40 and front anvil retainer 42,the forming punch 46 extends slightly into the ferrule opening 48 in adirection transverse to the axis of opening 48. When a ferrule isinserted into 48, it displaces forming punch 48 to the right (as seen inFIG. 4) against the biasing force of spring washer 52. This biasingforce urges the front anvil retainer 42 and consequently, the distal endof forming punch 46 toward the left to exert a non-deforming(non-crimping) frictional force on the ferrule located in opening 48.The frictional force exerted by forming punch 46 retains the ferrule inopening 48 with the axis of the ferrule extending generally transverseto the longitudinal axis of body 26; until the ferrule is applied to thelock wire.

Applicator 26 is connected to a power supply indicated schematically inFIG. 11. The power supply comprises a sump reservoir 56 containing anamount of a hydraulic fluid. Pump/motor 58 has inlet tube 60 extendinginto the sump 56 and an outlet conduit 62. The operation of thepump/motor 58 is controlled, in known fashion, by switch 64 mounted oncasing 28 of the applicator 26. Outlet conduit 62 is connected topressure cycle controller 66 which, in turn, controls the supply ofpressurized hydraulic fluid to tension cylinder 68 and to hydraulicsupply line 70. Hydraulic supply line 70 is connected to the proximalend of applicator 26 so as to communicate with chamber 34 via passage71.

Tension cylinder 68 has an extendable and contractable piston rod 72connected to bell crank 74 which is pivotally attached to a fixedstructure at 76. Bell crank 74 is also connected to flexible tension rod78, the opposite end of which is attached to tension rod 30 as seen inFIG. 4. Spring 80 biases the bell crank 74 in a counterclockwisedirection around its pivot attachment point 76. Hydraulic supply line 70and flexible tension rod 78 may be covered by a boot 79 extending fromthe applicator 26 to the power supply and formed of a flexible material.

Thus, as can be seen, when the pressure cycle controller 66 supplieshydraulic fluid to the tension cylinder 68 via conduit 69 causingextension of the piston rod 72 in the direction of arrow 82, bell crank74 will pivot in a clockwise direction about pivot attachment point 76,moving the flexible tension rod 78 in the direction of arrow 84. Asviewed in FIG. 4, this will move tension rod 30 toward the rightrelative to the casing 28 and the crimp head 44, thereby tensioning alock wire inserted into passage 30b.

Pressure cycle controller 66 has a known pressure relief/bypass valve 67to limit the hydraulic pressure that can be applied to tension cylinder68. Once this predetermined pressure limit has been reached, the excesshydraulic fluid is returned to the sump 56 via conduit 86. By limitingthe hydraulic pressure supplied to the tension cylinder 68, the amountof force imparted to flexible rod 78, tension rod 30, and, consequently,to the lock wire 20 will be limited to a predetermined value. Once thisvalue is reached, pressure activated valve 65 opens and pressurizedhydraulic fluid passes through line 70 into chamber 34 via passage 71and urges piston 36, piston rod 38 and rear anvil retainer 40 to theleft as shown in FIG. 4. The movement of the rear anvil retainer 40deforms the spring washer 52 and brings the rear anvil retainer 40 intodirect contact with front anvil retainer 42. Continued movement to theleft causes forming punch 46 to also move in this direction to apply acrimping force to a ferrule retained in opening 48. Gauges 75 and 77 maybe provided on the power supply to provide a visual indication of thetension and crimping pressures, respectively.

The magazine for retaining and inserting the ferrules into theapplicator 26 is illustrated in FIGS. 5, 6 and 7 and comprises amagazine body 86 with a tapered end portion 86a. Body 86 defines acentrally located, longitudinally extending opening 88 extendingcompletely along its length, as well as a longitudinally extending slot90. Slot 90 interconnects the opening 88 with the exterior surface ofthe body 86. As illustrated in FIG. 7, slot 90 may be tapered in aradially outwardly extending direction such that the distance betweenits innermost edges is less than the diameter of the opening 88.

The diameter of opening 88 is sufficient to slidably accommodate aplurality of axially aligned ferrules 92 therein. Opening 88 alsoslidably accommodates a feed rod 94 which bears against one end of thesupply of ferrules 92 and which is connected to handle 96. An elasticfriction element 98 is located around the end of body 86 and, asillustrated in FIG. 6, exerts a slight frictional force on the ferrule92 located closest to the end of body 86. This frictional force issufficient to retain the ferrules 92 in the body 86 as the device ismanipulated by the operator. Handle 96 and feed rod 94 are both slidablewith respect to the main body 86, but the interconnection has sufficientfrictional force to prevent the handle 96 and the feed rod 94 fromfalling out of the body 86 should it be manipulated into a verticalposition.

The process according to the invention is illustrated in FIGS. 8 and 9.As illustrated in FIG. 8, the magazine body 86 is placed against thecrimp head 44 such that the opening 88 is in alignment with opening 48.Handle 96 and feed rod 94 are axially displaced with respect to the body86 to force a ferrule 92 into the opening 48. As discussed previously,the ferrule 92 is frictionally retained in the opening 48 by the forceof spring washer 52 urging the forming punch 46 against the ferrule 92.This force is sufficient to retain the ferrule 92 into the opening 48,but is insufficient to cause any deformation of the ferrule.

When the ferrule has been loaded into the opening 48, the magazine isremoved from the applicator 26. The applicator 26 is manipulated suchthat lock wire 20 is threaded through the ferrule retained in theopening 48, through the notch 50 and through passage 30b formed intension rod 30, as shown in FIG. 9. The applicator 26 is thenmanipulated to a position wherein ferrule 92 bears against the side ofthreaded fastener 14 and the switch 64 is actuated. Preferably, thehousing 28 as illustrated is dimensioned so as to be manipulable by anoperator.

By actuating switch 64, hydraulic fluid is supplied to the tensioncylinder 68, which in turn, retracts the rod 30 further into the housing28 to exert a tension on lock wire 20. The notch 50 is curved such thatthe wire adjacent to the ferrule retained in the applicator is tensionedin a direction in approximately coaxial alignment with the opening inthe ferrule and the opening in the threaded fastener 14. Once thepredetermined tension has been applied to lock wire 20, forming punch 46is further displaced (toward to the left as viewed in FIG. 4) to deformthe ferrule and fixedly attach it to the lock wire 20. Forming punch 46is moved via its interconnection with front anvil retainer 42 which, atthis point, is in direct contact with the rear anvil retainer 40 movedby its connection with piston 36 through piston rod 38.

Once the ferrule has been sufficiently deformed, the punch 46 will bewithdrawn by reducing the hydraulic fluid pressure in chamber 34 and isretracted by the force exerted thereon by spring washers 54. Spring 39returns piston 36 and piston rod 38 to their initial positions shown inFIG. 4. The operation is completed by cutting off the lock wire 20downstream of the ferrule 92.

The foregoing description is provided for illustrative purposes only andshould not be construed as in any way limiting this invention, the scopeof which is defined solely by the appended claims.

What is claimed is:
 1. A process for connecting together a series ofelements, said series including a first and last element of the series,comprising:providing apertures in said elements for receiving a flexibletension element; threading an elongated flexible tension elementforwardly through said apertures serially from the first to the lastelement of the series; providing a first motion stopping means on afirst end of a flexible tension element for preventing forward movementof the tension element through the aperture in the first element in theseries; drawing a tension on the tension element in a forward directionfrom a location beyond the last element of the series while the firstmotion stopping means prevents forward movement of the tension elementrelative to the first element of the series; while maintaining saidtension on said flexible tension element, securing the tension elementagainst reverse longitudinal motion relative to the last element of theseries by providing a second motion stopping means permanentlyassociated with the tension element adjacent and beyond the last elementof the series, said second motion stopping means preventing reverselongitudinal movement of the tension means through the aperture of thelast element of the series, whereby the elements of the series areconnected together; wherein said elements are fasteners anchored to anobject through rotation of the fastener in a coupling direction whileengaging the object, and including the step of threading said tensionelement through each fastener aperture, whereby said fasteners areprevented from rotating in an uncoupling direction.
 2. A process asclaimed in claim 1 including permanently associating said first stoppingmeans with the tensioning element, whereby the fasteners of the seriesare permanently connected together so long as the tension elementremains intact.
 3. A process as claimed in claim 1 including providing apermanently deformable ferrule installed over the tension element assaid second motion stopping means, said step of permanently associatingthe second stopping means with the tension element including permanentlycrimping the ferrule onto the tension element.
 4. A process as claimedin claim 1 including tensioning said tension element up to apredetermined force before permanently associating said second motionstopping means with the tension element.
 5. A process as recited inclaim 3, including providing a combination tension element tensioningand ferrule crimping tool, the tool including a longitudinal axis andhaving proximal and distal ends, a tension element tensioner movablealong the longitudinal axis and arranged to exert a tension on thetension element by drawing the tension element toward the tool proximalend from the tool distal end, and a ferrule crimper movable along thetool longitudinal axis for crimping a ferrule retained within the toolat its distal end onto the tension element, said tool being manipulablefor placement of a distal end area of the tool and the ferrule adjacentthe last element or fastener of the series, and wherein the steps ofdrawing the tension on the tension element and crimping the ferruleincludes placing a ferrule in the tool, threading the tension elementthrough the ferrule and into engagement with the tension elementtensioner of the tool; activating the tensioner along the tool axis totension the tension element while the tool is manipulated to place thedistal end area of the tool against the last element or fastener of theseries to react the tension load; activating the tool ferrule crimperwhile the tension is maintained on the tension element by the tensionerto crimp the ferrule to the tension element adjacent the last element orfastener of the series, and removing the tool from the tension element.6. A process as claimed in claim 5, including placing and retaining theferrule in the tool so that the tension element must be threaded throughthe ferrule in a direction transverse to the tool longitudinal axis. 7.A process as claimed in claim 6 including retaining the ferrule in thetool by engaging the ferrule with the ferrule crimper while the crimperis located in a non-crimping ferrule gripping position before threadingthe tension element through the ferrule.
 8. A process for connectingtogether a series of elements, said series including a first and lastelement of the series, comprising:providing apertures in said elementsfor receiving a flexible tension element; threading an elongatedflexible tension element forwardly through said apertures serially fromthe first to the last element of the series; providing a first motionstopping means on a first end of a flexible tension element forpreventing forward movement of the tension element through the aperturein the first element in the series; drawing a tension on the tensionelement in a forward direction from a location beyond the last elementof the series while the first motion stopping means prevents forwardmovement of the tension element relative to the first element of theseries; while maintaining said tension on said flexible tension element,securing the tension element against reverse longitudinal motionrelative to the last element of the series by providing a second motionstopping means permanently associated with the tension element adjacentand beyond the last element of the series, said second motion stoppingmeans preventing reverse longitudinal movement of the tension meansthrough the aperture of the last element of the series, whereby theelements of the series are connected together; and including providing apermanently deformable ferrule installed over the tension element assaid second motion stopping means, said step of permanently associatingthe second stopping means with the tension element including permanentlycrimping the ferrule onto the tension element; and including providing acombination tension element tensioning and ferrule crimping tool, thetool including a longitudinal axis and having proximal and distal ends,a tension element tensioner arranged to exert a tension on the tensionelement by drawing the tension element toward the tool proximal end fromthe tool distal end, and a ferrule crimper movable generally parallel tothe tool longitudinal axis for crimping a ferrule retained within thetool at its distal end onto the tension element, said tool beingmanipulable for placement of a distal end area of the tool and theferrule adjacent the last element or fastener of the series, and whereinthe steps of drawing the tension on the tension element and crimping theferrule include placing a ferrule in the tool, threading the tensionelement through the ferrule and into engagement with the tension elementtensioner of the tool; activating the tensioner to tension the tensionelement while the tool is manipulated to place the distal end area ofthe tool against the last element or fastener of the series to react thetension load; activating the tool ferrule crimper while the tension ismaintained on the tension element by the tensioner to crimp the ferruleto the tension element adjacent the last element or fastener of theseries, and removing the tool from the tension element.
 9. A process asclaimed in claim 8, including placing and retaining the ferrule in thetool so that the tension element must be threaded through the ferrule ina direction transverse to the tool longitudinal axis.
 10. A process asclaimed in claim 9 including retaining the ferrule in the tool byengaging the ferrule with the ferrule crimper while the crimper islocated in a non-crimping ferrule gripping position before threading thetension element through the ferrule.
 11. A process for connectingtogether a series of elements, said series including a first and lastelement of the series, comprising:providing apertures in said elementsfor receiving a flexible tension element; threading an elongatedflexible tension element forwardly through said apertures serially fromthe first to the last element of the series; providing a first motionstopping means on a first end of a flexible tension element forpreventing forward movement of the tension element through the aperturein the first element in the series; drawing a tension on the tensionelement in a forward direction from a location beyond the last elementof the series while the first motion stopping means prevents forwardmovement of the tension element relative to the first element of theseries; while maintaining said tension on said flexible tension element,securing the tension element against reverse longitudinal motionrelative to the last element of the series by providing a second motionstopping means permanently associated with the tension element adjacentand beyond the last element of the series, said second motion stoppingmeans preventing reverse longitudinal movement of the tension meansthrough the aperture of the last element of the series, whereby theelements of the series are connected together; and wherein said elementsare fasteners anchored to an object through rotation of the fastener ina coupling direction while engaging the object, and including the stepof threading said tension element through each fastener aperture in adirection such that tension applied to the tension element in a forwarddirection urges at least one of the fasteners to rotate in a couplingdirection.